class Program
{
    static void Main(string[] args)
    {
        string inputWord = Console.ReadLine()!;
        int tCount = 0;
        int eCount = 0;
        int rCount = 0;
        int treeCount = 0;
        
        foreach (char c in inputWord)
        {
            if (c == 't')
            {
                tCount++;
            }
            else if (c == 'e')
            {
                eCount++;
            }
            else if (c == 'r')
            {
                rCount++;
            }

            if (tCount >= 1 &&  eCount >= 2 && rCount >= 1)
            {
                treeCount++;
                tCount--;
                eCount -= 2;
                rCount--;
            }
        }
        Console.WriteLine(treeCount);
    }
}